Vapor deposited zinc coated metallic substrates having organic coatings

ABSTRACT

METALLIC SUBSTRATES ARE PROVIDED WITH ADHERENT SURFACE FINISHES OF PAINTS, LACQUERS, PLASTICS AND THE LIKE BY THE USE OF INTERMEDITE ADHERENCE-PROMOTING VACUUM VAPOR DEPOSITED ZINC COATINGS.

s. T. WLODEK 3,674,445 VAPOR DEPOSITED ZINC COATED METALLIC SUBSTRATES July 4, 1972 HAVING ORGANIC COATINGS Filed May 13, 1968 Stanley WlodeK FIG. 2

ATTORNEY United States Patent 3 674 445 VAPOR DEPOSITED ZNMC COATED METALLIC SUBSTRATES HAVING ORGANIC COATINGS Stanley Thaddeus Wlodek, Bethel Park, Pa., assignor to 3,674,445 Patented July 4, 1972 ice radius of curvature of the bend is smallest at the location where the sample is bent about the mandrel adjacent to its apex and gradually increases to a maximum where the sample is bent about the mandrel adjacent to its base.

were bent in a conical mandrel test apparatus of the type described in ASTM Designation D522-60. Briefly, in this test the sample is formed about a conical mandrel so that a linearly extending bend is made along the sample. The

Jones & Laughlin Steel Corporation, Pittsburgh, Pa. 5 After the ples are formed, a length of edheslve P Filed May 13, 1968, Ser. No. 728,631 is applied along the length of the sample bend and then Int. Cl. B2311 3/00 rapidly removed. As can be understood, the tendency of US Cl- 29- 95 3 Claims the paint to part from the sample is greatest along the portion of the bend having the smallest radius of curvature since that is where the greatest amount of deforma- ABSTRACT OF THE DISCLOSURE tion has occurred and is least along the portion of the Metallic substrates are provided with adherent surface bend having the largest radius of curvature. Consequently, finishes of paints, lacquers, plastics and the like by the use the quality of paint adhesion can be determined by measof intermediate adherence-promoting vacuum vapor deuring from the end of the bend having the smallest rad us posited i coatings of curvature the length along the bend from which paint is peeled by action of the tape.

In the second technique, the Reverse Impact Technique, This invention relates to metallic substrates having ada p Plunger with a Spherical h is thrust against the herent functional and/or decorative surface finishes of Sample h its pf slde callslng a depression to h paints, lacquers, plastics and the like, a tight bond beformed In that e the sample Adheslve p 15 tween the finishes and the substrates being obtained b fastened to t named e of h sample Over the ethe use of intermediate vacuum vapor deposited zinc hke Pretmeleh formed 11! that slde 0f the Sample d 1S coatings then rapidly removed A series of such tests are carr ed Organic coatings are often provided on steel and other P 011 each sample With t f 0f the thrust mereeelhg metal substrates for corrosion prevention and other func- In each teet- The force In e -p 1mPaIted the tional purposes. The coatings are used also to provide h p by the p h at the tlme the Palht first beglns t0 decorative finishes. Generally, a metallic surface must Stlek the adheSlVe f l and P from the p e undergo extensive pretreatment to insure that the organic faee 15 noted along Wlth the depth of the depfesslefl coating will bond it lf tightly thereto draw formed by that force. These values represent a I have discovered that a tightly adherent organic coatmeasure of Palht adhereheeing can be provided on a metallic surface by interposing To mp e the adheslell 0f p h t0 Vacuum Vapor a vacuum vapor deposited zinc coating between the metalcPated h Wlth the adheeloh of lf to other yp of lie fa and the organic coating zinc coatings, samples of steel strip were galvanized by I have as an object of my invention to provide metallic Conventional hot'dlp eI1d eleethegelvflnlllhg l substrates having tightly adherent organic coatings. An- The Samples were then Palhted Wlth h Same y Paint other object of my invention is to provide such substrates e on e Vacuum Yapor coated 21116 ip and their wherein the bond between the organic coating and the Palht adhesloh t' y both the COIlleal Mandr l metallic surface is established by an intermediate vacuum and Reverse Impact e h order to determine the vapor d i d i coating relative effects of sub ecting the zinc coatings to prepaint These and other objects and advantages of my invention 40 treatments, the coatings Were Bondel'ized and then Painted will appear from the following description with reference with the Same Vinyl Paints and tested for Paint adhesion to the accompanying drawing in which: quality. The results of these tests are tabulated below:

Reverse impact Conical mandrel Prepaint (peel length- Coating treatment Force (in.-ibs.) Draw (miL) inches) vawumvworzhc fi hahaaz ii? iii '8 Home the hfiiaa'zaai'. 2 3 3:8 electrogalvanized ggfiiahzaai. 3 23 3:3

FIG. 1 is an electron microscope photogram of the sur- From the table it can be seen that the paint adhesive 'face of a vacuum vapor deposited zinc coating taken at properties of hot-dip zinc and electrogalvanized coatings 8,750 diameters. which have not been treated are extremely poor. The FIG. 2 is an electron microscope photogram of the sursamples used in the Conical Mandrel test were six inches face of a hot-dip zinc coating taken at 8,750 diameters. long, and as the table indicates, the paint parted from the Cold rolled steel strip was coated with zinc by vaporizhot-dip and electrogalvanized coatings along the entire ing the zinc in an evacuated chamber in which the strip length of the bend. The Reverse Impact test results indicate was placed and condensing the zinc vapor on it. The dethe fact that the paint peeled from the hot-dip and electrotails of the zinc coating process are not part of the present galvanized coatings in the absence of the application of invention and are familiar to those skilled in the art of any force. The untreated vacuum vapor deposited zinc vacuum vapor coating. coatings on the other hand demonstrated paint adhesive Samples of strip so coated were then painted with a properties such as to make them useful' for promoting vinyl paint and paint adhesion determined. The quality of the adhesion of organic coatings to metallic substrates in the paint adhesion was determined by two techniques. In commercial application. Subjecting the samples to a conthe first, the Conical Mandrel Technique, the samples ventional bonderizing treatment improved paint adhesion somewhat for all the coatings but the adhesion of the paint to the vacuum vapor deposited zinc coatings was still significantly improved over the hot-dip and electrogalvanized coatings.

Improved adhesion to steel substrates provided with intermediate vacuum deposited zinc coatings has also been obtained for paints containing alkyds, acrylics, silicones, epoxies and mixtures thereof. The reasons why vacuum deposited zinc coatings promote the adhesion of organic coatings to metallic substrates appear to be at least twofold. First, the zinc coatings because they are deposited by what amounts to a distillation process have extremely clean and pure surfaces, i.e., surfaces free of contaminants, inclusions and the like, and second, the vacuum deposited zinc coatings include a multitude of minute crystal surfaces which create sites to which the organic coatings can mechanically lock. The surface of the hot-dip zinc coating shown in FIG. 2 includes impurity inclusions 1-1 at grain boundaries and oxides 2-2 over the whole surface, which mitigate against good organic coating adhesion. In addition, the surface is relatively smooth. The surface of the vacuum deposited zinc coating shown in FIG. 1 is clean and is free of adherence-ofisetting second phases. Also the surface has a microroughness which is of some depth so as to enable the organic coatings to lock onto the zinc coating.

Because it is the nature of the zinc coating surface which is primarily responsible for promoting organic coating adhesion to an underlying metallic base, it will be appreciated that vacuum deposited zinc coatings can be employed to promote organic coating adhesion to substrates of steel, aluminum, copper and other metallic bases to which the zinc can be made to adhere.

The thickness of the zinc coating is not critical in promoting organic coating adhesion, and I have found that zinc thicknesses of as low as 0.1 mil can be employed. Generally, a minimum zinc coating thickness of about 0.5 mil is required if it is desired that the zinc provide corrosion protection to the underlying metallic base.

I claim:

1. An article of manufacture comprising a metallic substrate, av vacuum vapor deposited coating of zinc on said substrate and an adherent organic coating on said ZlIlC.

2. An article as recited in claim 1 wherein the zinc coating is about 0.1 mil thick.

3. An article as recited in claim 1 wherein the substrate is selected from the group consisting essentially of steel, aluminum and copper.

4. An article as recited in claim 3 wherein the organic coating is selected from the group consisting of paints, plastics and lacquers.

5. An article as recited in claim 1 wherein the substrate is steel.

6. An article as recited in claim 5 wherein the organic coating is selected from the group consisting of plaints, plastics and lacquers- 7. An article as recited in claim 5 wherein the organic coating is a paint selected from the group consisting of epoxies, vinyls, silicones, acrylics, alkyds and mixtures thereof.

8. An article as recited in claim 7 wherein the paint is a vinyl.

References Cited UNITED STATES PATENTS 2,812,270 11/1957 Alexander 117-107 X 2,993,806 7/1961 Fisher et a1. 117-107 X 3,278,331 10/1966 Taylor et a1. 11771 M X 3,326,177 6/1967 Taylor ll7107 X ALFRED L. LEAVITT, Primary Examiner C. K. WEIFFFENBACH, Assistant Examiner US. Cl. X.R. 11771 M, 107 

